Heat transfer surfaces



March 27, 1962 R. D. VAUGHAN HEAT TRANSFER SURFACES 2 Sheets-Sheet 1 Filed. Nov. 25. 1957 R. D. VAUGHAN HEAT TRANSFER SURFACES March 27, 1962 2 Sheets-Sheet 2 Filed NOV 25. 1957 3,927,314 AT TRANSFER SURFACES Roger D. Vaughan, Newcastle-upon-Tyne, England, as-

signor to C. A. Parsons 8; Comp-any Limited, Newcastle-upon-Tyne, England Filed Nov. 25, 1957, Ser. No. 698,635 Claims priority, application Great Britain Nov. 28, 1956 3 Claims. (Cl. 204-4932) This invention relates to a tubular heat exchange element comprising a tube having helical fins disposed on a peripheral surface, flow channels formed between the fins being interrupted by baflles extending longitudinally of the element.

In application No. 618,258, having the same assignee as the present application, is described a tubular heat exchange element suitable for use as a fuel container for nuclear fuel in a nuclear reactor the form of element described consisting of a container for nuclear fuel the outside surface of which had helically disposed fins, the fiow channels formed between the fins being interrupted at certain places by longitudinal baffies, the baffies being equally spaced over the periphery of the element.

It becomes necessary in practice to fix the baffles in position and yet allow for a certain degree of ditfrential expansion between bafile and container. In addition it is necessary that the flow path for the fluids entering the flow channels between the fins should be substantially uninterrupted by the fixing means for the bafiies.

The object of the present invention is to provide fixing means for the baffles which substantially meet these requirements.

In a heat exchange element according to the present invention, the tube has helical fins spaced around the peripheral surface with the fiow channels formed between the fins interrupted by bafiles extending longitudinally of the element, and the baffles are loosely inserted in longitudinal slots formed in the fins and held in position by rings detachably secured to the tips of the fins at either end of the element and engage with a clearance slots formed in the ends of the bafiles. In a preferred form of the invention, the rings are screwed onto the fins.

Referring to the accompanying diagrammatic drawings:

FIGURE 1 shows in section an end portion of two fuel elements for a nuclear reactor;

FIGURE 2 shows an end view of one such element.

In carrying the invention into effect in the form illustrated in FIGURES l and 2 by way of example each element consists of a container 1 having spaced fins 2 helically disposed about its longitudinal axis XX. Interrupting the spaces between the fins are longitudinal baffles 3 which loosely fit into slots formed in the fins. In the form illustrated four such baffies are associated with each element the baffles being equally spaced apart over the circumference of the element.

Nuclear fuel 4 is housed in the container 1 and is kept in position in the container by end caps 5 which are welded to the ends of the container and are separated from the fuel by heat insulating discs 6.

In the form illustrated these end caps 5 are screwed in turn to end fittings 7 which are conical in form so as 3,@Z7,3l4 Patented Mar. 27, 1962 to assist accurate location of the elements when they are being stacked one upon the other in a channel in the reactor.

The fixing means for the baffles 3 comprise a ring 8 which is screwed to the tips of the fins and fits with a clearance into a slot 9 in each bafile. This clearance allows for expansion of the baflie relative to the container in an axial direction.

Movement of the bafiies in a radial direction is, however, prevented by the ring 8.

With the arrangement shown the flow of gas through the fins and between the baffies is substantially unimpeded by the fixing ring.

The ring is preferably made of material having low neutron absorption properties such as a magnesium alloy.

A further advantage of the invention is that the ring protects the ends of the fins against damage during use particularly during the charging or discharging operation for the elements.

In addition the rings may be fixed in position after the end fixings are attached, so that they are completely independent of the actual form of seal and end-fixing employed.

Whilst the invention has been described with particular reference to fuel elements for nuclear reactors, it is applicable to all tubular heat exchange elements of the kind described.

I claim:

1. A tubular heat exchange element comprising a tube having helical fins disposed on a peripheral surface, flow channels formed between the fins being interrupted by baffies spaced around the periphery and extending longitudinally of the element, in which element the bafiies are loosely inserted in longitudinal slots formed in the fins and are held in position by rings detachably secured to the tips of the fins at each end of the element and engaging with a clearance slots formed in the ends of the baffies.

2. A tubular heat exchange element as claimed in claim 1, in which a ring is screwed onto the tips of the fins.

3. A tubular heat exchange element as claimed in claim 1, in which the tube contains nuclear fuel and the element forms a fuel element in a nuclear reactor.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Nucleonics, vol. 13, No. 6, June 1955, page 93. in Div. 46.)

International Conferences on the Peaceful Uses of (Copy in (COPY Atomic Energy, vol. 9, pp. 221-230, 1955. Scientific Library.) 

1. A TUBULAR HEAT EXCHANGE ELEMENT COMPRISING A TUBE HAVING HELICAL FINS DISPOSED ON A PERIPHERAL SURFACE, FLOW CHANNELS FORMED BETWEEN THE FINS BEING INTERRUPTED BY BAFFLES SPACED AROUND THE PERIPHERY AND EXTENDING LONGITUDINALLY OF THE ELEMENT, IN WHICH ELEMENT THE BAFFLES ARE LOOSELY INSERTED IN LONGITUDINAL SLOTS FORMED IN THE FINS AND ARE HELD IN POSITION BY RINGS DETACHABLY SECURED TO THE TIPS OF THE FINS AT EACH END OF THE ELEMENT AND ENGAGING WITH A CLEARANCE SLOTS FORMED IN THE ENDS OF THE BAFFLES. 